Facebook’s sites and apps, including Instagram and WhatsApp, were experiencing outages globally for millions of users on Wednesday.

The social media giant spent several hours unsuccessfully trying to resolve the outage.

“We're focused on working to resolve the issue as soon as possible, but can confirm that the issue is not related to a DDoS attack,” or Distributed Denial-of-Service, referring to a hackers’ attack, Facebook tweeted about 3 p.m. Wednesday, adding that the company was working to resolve the problem as soon as possible.

The website DownDetector.com said Facebook began having issues at about noon Eastern time.

Direct messages on Facebook and Instagram appeared to be largely unaffected.

“As with nearly every Facebook outage, users headed to Twitter with the hashtag #facebookdown quickly becoming the top trending topic in the United States,” according to USA Today.

The Verge tested Facebook’s ad platform and found problems there, too. “Facebook’s ad section was not functioning either, and it led to an internal error when you tried to buy an ad,” the website reported.